Does tuberculosis top HIV/AIDS as the deadlier disease?

Among nations, the United States is the runaway leader in the money it spends on global health programs, and the looming question for advocates is what will happen under President Donald Trump and a Republican Congress. Nick Seymour, a Harvard junior volunteering at a health clinic in Mexico, argued for sustained spending.

"One would be hard-pressed to find a policy issue that has a greater impact on more lives than global health financing, yet the topic has not broken through the white noise of the election and post-election coverage," Seymour wrote in a Jan. 7 op-ed published in The Hill.

Seymour underscored the many millions of HIV/AIDS patients helped by American dollars, and noted a disturbing trend with tuberculosis.

"Tuberculosis’ recent surpassing of HIV/AIDS as the leading infectious killer globally has not been met with anything close to equal funding for relief," he wrote.

We’ve looked at TB’s death toll before; it is a wickedly tenacious disease. The data question is, has it really become a bigger killer than HIV/AIDS?

And looking at the data, the estimates are mixed. But just as importantly, the relative death tolls of the two diseases has more to do with success in treating HIV/AIDS patients, and less to do with any change in the spread of TB.

Seymour told us he relied on figures from the United Nations and World Health Organization. For 2015, they estimated 1.1 million people died from HIV/AIDS. In the same year, TB deaths reached 1.4 million, jumping 300,000 from just a year before.

The rise inspired headlines that tuberculosis was now the leading cause of death from infectious disease. And within the framework of that UN data, that was accurate.

But there is another widely used and well regarded overview of global health. It is the Global Burden of Disease study, produced by the Institute for Health Metrics and Evaluation at the University of Washington and published by the British medical journal Lancet.

By their calculations, TB deaths in 2015 totalled 1.1 million and HIV/AIDS deaths 1.2 million. But as institute researchers Hmwe Kyu and Theo Vos, told us, you couldn’t actually say that one topped the other.

"We didn’t find any statistically significant difference between the number of deaths due to both diseases," they said.

An imperfect science: The India factor

Estimating deaths from TB and HIV/AIDS requires judgment calls. As the WHO’s TB report noted in its methodology section, "There are many potential sources of uncertainty associated with estimates of TB incidence, prevalence and mortality."

Many poorer, more rural nations have a hard time collecting the data from doctors and clinics. Faced with missing numbers, analysts make assumptions to fill in the gaps. Then they run the country totals through overall statistical models that involve other assumptions.

Usually, the Institute for Health Metrics and Evaluation and the WHO roughly agree at the global level. But in 2015, there was a 300,000 death difference for TB.

That was also the first year when new numbers from India began to change the WHO’s global estimates.

Prudence Smith, a WHO spokeswoman, told us in October that between 2013 and 2015, India shifted from a reporting system based on paper to one that lives on the Internet.

"In addition," Smith said, " the country has made case notification legally mandatory."

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In the world of tuberculosis, India is a huge deal. It is home to more than 25 percent of all TB cases and deaths worldwide.

With more raw data in hand, the WHO’s estimate of the TB death toll in India more than doubled, going from 220,000 in 2014 to 480,000 in 2015, a jump of 260,000.

To be clear, it’s not that more people were dying from TB, just that India reported more deaths to the WHO.

Curiously, in the same period, the institute’s estimate for India barely changed. It had judged the figure to be in the neighborhood of 480,000 since 2013.

The WHO’s upward shift for India accounted for 80 percent of the rise in its global total for TB. The institute had no reason for such an adjustment. It had factored in a higher number for India all along and it's global total remained about the same.

Why TB might overtake HIV/AIDS (without even trying)

Most people hearing that TB deaths now outnumber HIV/AIDS deaths, or had simply pulled even with HIV/AIDS, would likely think that TB was spreading. That would be wrong.

Beyond the matter of better reporting out of India and a couple of other countries, the real driver behind the shifting numbers has to do with HIV/AIDS.

"We have been much more successful in the fight against AIDS than TB," said Audrey Jackson, a senior global health fellow at the Center for Strategic and International Studies. (Jackson just published a report on the many ways TB programs have played second fiddle inside Washington.)

Death rates for both TB and HIV/AIDS have been falling, but the decline has been faster for HIV/AIDS than TB.

Using the institute's data, between 2005 and 2015, the death rate for HIV/AIDS globally fell by 42 percent. At the same time, the TB death rate fell by about 34 percent. This chart from the institute’s database shows the impact on the number of deaths.

The gains against HIV/AIDS have a lot to do with a massive hike in the number of people receiving antiretroviral treatment.

There has also been a rise in the number of people getting treated for TB, but according to researchers at the Institute for Health Metrics and Evaluation, in many countries, it’s proven harder to spot patients with TB. That leads to delays in care, which in turn make it harder for the person to beat the disease. Couple that with the rise in antibiotic resistant TB, along with other factors, and the gains are slower compared to HIV/AIDS.

Those trends cast TB as more of a growing threat than HIV/AIDS. Right now, the death rates are about the same. However, Hmwe Kyu at the institute said that if the trend lines continue, then the victims of TB will outnumber those of HIV/AIDS.

Not because TB has become worse, but because the situation with HIV/AIDS got better faster.

Our ruling

Seymour said tuberculosis is now a bigger killer than HIV/AIDS. Numbers from the United Nations and the World Health Organization support that, but another equally credible source, the Institute for Health Metrics and Evaluation at the University of Washington, said the death tolls are about the same. The data’s not good enough for highly precise estimates.

It’s also unclear that TB is killing more people than it did before. The higher estimate by the WHO reflects better reporting, mainly from India, but not more actual deaths.

The one undisputed point is that death rates are falling faster for HIV/AIDS than for TB. Both sets of data back that up. In that respect, TB is the more threatening infectious disease because the world is having a harder time getting ahead of it. But that doesn't necessarily mean that the TB threat is itself rising. It looms larger than HIV/AIDS because that threat has fallen.

On balance, we rate this statement Half True.